System and method for reutilizing co2 from combusted carbonaceous material

ABSTRACT

A system for generating steam supplies of coal another material to one or more processing chambers. Each processing chamber includes a plasma arc torch that heats the material in the presence of water and a treatment gas at an extremely high temperature. A product gas stream is delivered from each processing chamber to a heat recovery steam generator (HRSG). Each HRSG generates steam that is used to drive a steam turbine. The processing chambers and HRSGs are fluidly connected so that the product gas streams moves from a processing chamber, to a HRSG, to another processing chamber, and then to another HRSG, etc. Within any of the HRSGs, or after the final HRSG, water in the product gas may condense to liquid water that may be redirected to any of the processing chambers. In addition, CO 2  from the final HRSG may be redirected into any of the processing chambers to facilitate further reactions in the chambers.

RELATED APPLICATIONS

This application claims priority to U.S. provisional patent applicationNo. 61/330,729 filed May 3, 2010, the entire contents of which areincorporated by reference herein.

BACKGROUND

The present disclosure relates to the generation of steam resulting fromthe combustion and processing of carbonaceous material for thegeneration of electricity and other uses.

Despite the serious problems caused by its use, coal is cheap andplentiful and will not be abandoned as an energy source any time soon.According to the Pew Center for Global Climate Change, coal use,primarily for the generation of electricity, now accounts for roughly 20percent of global greenhouse gas emissions. Rising energy demand willcontinue to drive up coal consumption, particularly in countries withlarge reserves such as the United States, China and India.http://www.pewclimate.org/global-warming-basics/coalfacts.cfm.

Coal can provide usable energy at a cost of between $1 and $2 per MMBtucompared to $6 to $12 per MMBtu for oil and natural gas, and coal pricesare relatively stable. At current consumption rates and with currenttechnology and land-use restrictions, the U.S. coal reserves would lastwell over 250 years. Although coal is higher-polluting and morecarbon-intensive than other energy alternatives, coal is so inexpensivethat one can spend quite a bit on pollution control and still maintaincoal's competitive position.

Coal plays a major role in meeting U.S. energy needs, and is likely tocontinue to do so in coming decades. About fifty percent of theelectricity generated in the United States is from coal. U.S. coal-firedplants have over 300 GW of capacity, but approximately one-third of theU.S. coal-fired plants date from 1970 or earlier, and most of the restfrom 1970-1989. Only twelve coal-fired plants have been built in theUnited States since 1990.

Greenhouse gas emissions from coal-fired power are significant andgrowing rapidly. The United States has been estimated to produce closeto 2 billion tons of CO₂ per year from coal-burning power plants.Greenhouse gas emissions from coal-fired electricity, now 27 percent oftotal U.S. emissions, are projected to grow by a third by 2025.

SUMMARY

A method of generating steam comprises providing a continuous supply ofcoal, combusting the coal in a primary processing chamber in thepresence of oxygen and water to provide a first product gas stream,recovering heat from the first product gas stream in a first heatrecovery steam generator (HRSG) to produce a first steam output,processing the first product gas stream in a secondary processingchamber in the presence of oxygen and water to provide a second productgas stream substantially free of inorganic, organic and particulatecontaminants, recovering heat from the second product gas stream in asecond heat recovery steam generator (HRSG) to produce a second steamoutput, and combining the first steam output and the second steamoutput. The combined steam output may be used to drive a steam turbine.In certain embodiments, the steam turbine is operatively coupled to anelectric generator to produce electricity. In certain embodiments, themethod further comprises at least one of reducing the temperature of thesecond product gas stream, treating the second product gas stream by wetscrubbing, separating sulfur from the second product gas stream andcollecting the sulfur with a baghouse, using a carbon dioxide recoverysystem, and discharging a treated gas stream substantially free ofcontaminants.

Other embodiments of the method comprise providing a continuous streamof thermal waste gas, recovering heat from the thermal waste gas streamin a first heat recovery steam generator (HRSG) to produce a first steamoutput, processing the thermal waste gas stream in a primary processingchamber in the presence of oxygen and water to provide a product gasstream, recovering heat from the first product gas stream in a secondheat recovery steam generator (HRSG) to produce a second steam output,and combining the first steam output and the second steam output. Incertain embodiments, the combined steam output is used to drive a steamturbine. In certain embodiments, the steam turbine is operativelycoupled to an electric generator to produce electricity. In certainembodiments, the method further comprises reducing the temperature ofthe product gas stream, treating the product gas stream by wetscrubbing, separating sulfur from the second product gas stream andcollecting the sulfur with a baghouse, and discharging a treated gasstream substantially free of contaminants.

Certain embodiments provide a system for generating steam comprising aprimary processing chamber having at least one plasma arc torch, theprimary processing chamber being operatively connected to a continuouscarbonaceous material feed, a treatment gas source and a water source,wherein the primary processing chamber is fluidly connected to a firstheat recovery steam generator that is fluidly connected to a steamturbine. In certain embodiments, the system further comprises asecondary processing chamber having at least one plasma arc torch, thesecondary processing chamber being fluidly connected to the first heatrecovery steam generator, a treatment gas source and a water source,wherein the secondary processing chamber is fluidly connected to asecond heat recovery steam generator that is fluidly connected to thesteam turbine. In some embodiments, the carbonaceous material is thermalwaste gas. In some embodiments, the carbonaceous material is selectedfrom the group consisting of coal, oil, natural gas, and oil shale,biomass, coke, petroleum coke, char, tars, wood waste, methanol,ethanol, propanol, propane, butane, and ethane. In some embodiments, thesecond heat recovery steam generator is fluidly connected to at leastone of a quench chamber, a wet scrubber, a baghouse or a carbon dioxideremoval system.

Other embodiments of the system comprise a programmable two-way valvewith an input in fluid connection with the wet scrubber and two outputs,one in fluid connection with the baghouse and the other in fluidconnection with the primary processing chamber, the latter configured toreturn at least a portion of the carbon dioxide from the effluent of thewet scrubber to the primary processing chamber. In some embodiments,process parameters are monitored by a plurality of monitors, each ofsaid monitors providing data related to the process parameters to aprocessor. In certain embodiments, the process parameters comprisetemperature, pressure, and carbon dioxide content. In certainembodiments, the processor controls the programmable two-way valvethrough an actuation mechanism via a control mechanism. In certainembodiments, the processor comprises a tangible memory containingcomputer readable instructions for the processor to follow.

In certain embodiments, the system further comprises a secondprogrammable two-way valve with an input in fluid connection with thewet scrubber. In certain embodiments, the system further comprises asecond programmable two-way valve with an input in fluid connection withone of the two heat recovery steam generators. In certain embodimentsthe second programmable two-way valve comprises two outputs, one influid connection with a waste water treatment and/or discharge facilityand the other in fluid connection with the primary processing chamber orthe primary processing chamber water source. In some embodiments,process parameters are monitored by the plurality of monitors, each ofsaid monitors providing data related to the process parameters to aprocessor. In certain embodiments, the process parameters comprisetemperature, and water flow rate from the primary processing chamberwater source. In certain embodiments, the processor controls the secondprogrammable two-way valve through a second actuation mechanism via asecond control mechanism.

Certain embodiments provide a method of generating steam comprisingproviding a continuous supply of a carbonaceous material, combusting thecarbonaceous material in a first processing chamber having at least oneplasma arc torch in the presence of oxygen and water to provide a firstproduct gas stream; recovering heat from the first product gas stream ina first heat recovery steam generator to produce a first steam output;processing the first product gas stream in a second processing chamberhaving at least one plasma arc torch in the presence of oxygen and waterto provide a second product gas stream substantially free of carbonmonoxide and hydrogen, recovering heat from the second product gasstream in a second heat recovery steam generator to produce a secondsteam output; and using the first steam output and the second steamoutput. Typically, method comprises using the first steam output and thesecond steam output to operate a steam turbine. In some embodiments, thefirst steam output and the second steam output operate a steam turbineoperatively connected to an electric generator to produce electricity.

In certain embodiments, the method comprises one or more of the steps ofquenching the second product gas, processing the second product gas witha wet scrubber, processing the second product gas with a baghouse, andprocessing the second product gas with a carbon dioxide removal system.

In certain embodiments, the method further comprises diverting at leasta portion of the carbon dioxide in the second product gas to the primaryprocessing chamber via a programmable two-way valve. In someembodiments, the programmable two-way valve is under process control viaa control mechanism that is actuated by a processor. In someembodiments, the processor comprises a tangible memory containingcomputer readable instructions for the processor to follow. In someembodiments, the process control is based at least in part on datasupplied to the processor by a plurality of monitors, each of saidmonitors providing data related to at least one of a plurality ofprocess parameters. In some embodiments, the process parameters comprisepressure, temperature, and carbon dioxide content in a product gas.

In certain embodiments, the method further comprises diverting at leasta portion of the water in the second product gas to the primaryprocessing chamber or to the primary processing chamber water source viaa second programmable two-way valve. In some embodiments, the methodfurther comprises diverting at least a portion of the water from eitherof the two heat recovery steam generators to the primary processingchamber or to the primary processing chamber water source via a secondprogrammable two-way valve. In some embodiments, the second programmabletwo-way valve is under process control via a second control mechanismthat is actuated by the processor. In some embodiments, the processcontrol is based at least in part on data supplied to the processor bythe plurality of monitors, each of said monitors providing data relatedto at least one of the plurality of process parameters. In someembodiments, the process parameters comprise pressure, temperature, andwater flow from the water source to the primary processing chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of thedisclosure will be apparent from the following more particulardescription of various embodiments of the disclosure, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the disclosure.

FIG. 1 is a flow-chart showing an exemplary embodiment of a systemaccording to the present disclosure having two heat recovery steamgenerators (“HRSGs”).

FIGS. 2A-C are flow-charts showing alternative exemplary embodiments ofthe system of FIG. 1 further comprising an electric generator, a quenchchamber, a wet scrubber, a carbon dioxide recycling system, and a waterrecycling system.

FIG. 3 is a flow-chart showing an alternative exemplary embodiment ofthe systems of FIGS. 2A and B further comprising an absorption boiler.

FIG. 4 is a flow-chart showing an alternative exemplary embodiment ofthe systems of FIGS. 2A-C in which the baghouse is upstream of the wetscrubber.

FIG. 5 shows a Sankey diagram for one exemplary baseline two-HRSGembodiment of a system according to the present disclosure.

FIG. 6 shows a Sankey diagram for another exemplary two-HRSG embodimentof a system according to the present disclosure.

FIG. 7 shows a Sankey diagram for another exemplary two-HRSG embodimentof a system according to the present disclosure.

FIG. 8 shows a Sankey diagram for another exemplary two-HRSG embodimentof a system according to the present disclosure.

FIG. 9 shows a Sankey diagram for another exemplary two-HRSG embodimentof a system according to the present disclosure.

FIG. 10 is a flow-chart showing an alternative exemplary embodiment ofthe system that is useful for treating a thermal waste gas stream.

FIGS. 11A and 11B are schematic diagrams of a non-transferred modeplasma arc torch, and a transferred mode plasma arc torch.

FIG. 12 is a schematic diagram of a processing chamber having atransferred mode plasma arc torch and a centrifuge.

FIG. 13 is a schematic diagram of an embodiment of a vertical processingchamber layout having primary and secondary processing chambers and twoHRSGs according to the present disclosure.

FIGS. 14A, 14B and 14C are schematic diagrams of an embodiment of ahorizontal processing chamber layout for primary and secondaryprocessing chambers and two HRSGs according to the present disclosure,showing a cross-section view, FIG. 14A with a modular plasma-arccentrifugal treatment system (PACT), a longitudinal section view, FIG.14B and cross-section view, FIG. 14C with a plurality of modular PACTs.

DETAILED DESCRIPTION

The present disclosure is directed to a method and system for generatingsteam from coal for the generation of electricity and other uses. Theterm “coal,” as used herein, is intended to refer to any carbonaceousfeedstock, such as wood chips or organic waste, of adequate carbondensity. As used herein, the term “carbonaceous material” refers to anysolid, liquid or gaseous carbon-containing material suitable for use asa fuel, i.e. a material which can be combusted to produce energy.Included within the scope of this term are fossil fuels, including coal,oil, natural gas, and oil shale, biomass, i.e. plant materials andanimal wastes used as fuel, coke, petroleum coke (“petcoke”), char,tars, wood waste, thermal waste gas, methanol, ethanol, propanol,propane, butane, ethane, etc. In certain embodiments, the coal is abituminous coal.

This disclosure is not limited to the particular methodologies, systemsand materials described, as they may vary. Also, the terminology used inthe description is for the purpose of describing the particular versionsor embodiments only, and is not intended to limit the scope. Forexample, as used in this document, the singular forms “a,” “an,” and“the” include plural references unless the context clearly dictatesotherwise. The word “comprising” as used herein is intended to mean“including but not limited to.” Unless defined otherwise, all technicaland scientific terms used herein have the same meanings as commonlyunderstood by one of ordinary skill in the art.

According to the system and method of the present disclosure, coal iscombusted in the presence of oxygen and water and to generate a hotproduct gas stream, from which heat is extracted to produce steam foruses including, but not limited to, driving a turbine operatively linkedto an electric generator for the production of electricity. After theheat is extracted, the product gas stream is treated to remove themajority of contaminants. This treatment produces a “clean” carbondioxide stream that meets Environmental Protection Agency (“EPA”)emission regulations, and can be used, for example, in chemicalprocesses, for EPA approved sequestration, and the like.

The disclosed apparatus and method of operation enable combustion atvery high temperatures for the direct and efficient exploitation of theheat produced to generate steam and the processing of the combustionproducts enabling efficient and convenient management of environmentallyunfriendly byproducts of the combustion.

The method includes providing a continuous supply of coal, combustingthe coal in a primary processing chamber (PPC) that provides circulationof gaseous reactants, recovering the heat that is the result of thecombustion in a heat recovery steam generator (HRSG) to producehigh-pressure steam. Complete combustion of the coal is accomplished bycombining the coal with oxygen and water in a high-temperature plasmareactor.

Processes for gasifying coal to produce synthetic gas (“syngas”) areknown. The purpose of such gasification processes is to increase or atleast maintain the caloric content of the syngas relative to the coalstarting material. The syngas is then burned for generate steam to drivea turbine, for electricity generation. However, in the method of thepresent invention, instead of burning the product gas that results fromthe combustion of coal in the presence of oxygen and water, the heatfrom the product gas is used to convert water to steam, which in turn isused, in some embodiments, to drive a turbine operatively linked to anelectric generator to produce electricity.

Embodiments of the method may include multiple stages through which theproduct gas stream passes sequentially, with each stage comprising aprocessing chamber or reactor and a heat recovery steam generator(HRSG), with the HRSG downstream relative to the processing chamber. Theproduct gas output from the final (furthest downstream) HRSG isprocessed through further steps comprising quenching, wet scrubbing andbaghouse filtration, as needed, which result in a gas stream that issuitable for convenient management. Equipment for the practice of thedisclosed method is commercially available from several suppliers. Incertain embodiments, a suitable processing chamber or reactor is aplasma-arc centrifugal treatment (“PACT”) system built by Retech SystemsLLC (Ukiah, Calif.), and a suitable heat recovery steam generator (HRSG)system is built by NEM Standard Easel (Hengelo, Netherlands), and/orothers.

Various embodiments of the systems and methods of the present disclosurecan process coal in a continuous stream instead of batches, efficientlyextract heat from the gas produced by the combustion of the coal in thepresence of oxygen and water to create steam to drive a stream turbine,require about fifty (50%) percent less coal than other coal fired powerplants to achieve similar electrical power levels; remove contaminantefficiently removal from gas streams, produce and capture a clean carbondioxide stream ready for EPA approved sequestration.

Embodiments of the system and method will now be described withreference to the Figures. FIG. 1 is a flow-chart illustrating oneexemplary system 1 comprising a combustion section A operativelyconnected to a power generating section B and a gas decontaminationsection C.

As shown, combustion section A comprises a primary processing chamber 10(“PPC 10”), first heat recovery steam generator 20 (“first HRSG 20”), asecondary processing chamber 30 (“SPC 30”), a second HRSG 40. In certainembodiments, the gas decontamination section C comprises one or more ofthe following components: a quench chamber 50, a baghouse 70, a wetscrubber 60, and a CO₂ removal system 120, all fluidly connected. Asource of a treatment gas 80, 90 (such as O₂), and source of water 85,86, are both fluidly connected to each of the primary and secondaryprocessing chambers 10, 30, respectively. The treatment gas 80 and thetreatment gas 90 may be the same or different. In certain embodiments,treatment gas 80 and treatment gas 90 comprise 93-95% oxygen and 5-7%argon.

The PPC 10 receives a continuous coal feed 75 as well as the treatmentgas input 80 and water input 85, and outlets 16 and 18 for slag and gas,respectively. The PPC 10 is capable of withstanding the processingconditions (i.e., temperature, pressure, corrosion, and the like) underwhich the combustion of coal in the presence of oxygen and water takesplace. One exemplary system is a plasma arc centrifugal treatment (PACT)system available from Retech Systems, LLC, in Ukiah, Calif., whichcomprise at least one plasma arc torch. For ease of discussion, theterms “torch” or “torches” will be used hereinafter to refer to plasmaarc torches. The torches are capable of reaching temperatures ranging ofup to about 10,000° F. to about 20,000° F. (about 5,540° C. to about11,080° C.), or more. In various embodiments, the PPC may rotate tofacilitate distribution of the combustion materials to the torch in thechamber.

There are two types of plasma torches differing in their structure andthe mode in which they operate, as shown in FIGS. 11A and 11B. Thefirst, a transferred-arc torch, is effective at heating the work piece,and operates by drawing the arc between the torch and the work piece(the molten slag) with the work piece acting as the cathode. The second,a non-transferred-arc torch, is especially effective in heating the gas.In non-transferred-arc torches, the torch houses both the anode and thecathode, and the cathode is downstream of the anode. In operation, thearc is drawn within the torch, and the plasma extends beyond the end ofthe torch as a result of high gas flow through the torch, even thoughthe electrodes are inside the torch. One exemplary PACT system comprisesone or more non-transferred arc plasma torches fitted with gas backflowcollars.

In certain embodiments, the method involves continuously introducingcoal into the PPC 10, with the treatment gas 80 simultaneously suppliedto chamber 10 at a predetermined flow rate and concentration to ensurecomplete combustion of the coal, while the chamber rotates and thetorches heat both the coal and the treatment gas contained in thechamber. The ability to feed and operate the process continuously is animportant virtue, improving both efficiency and the continuity of theoutput electrical power.

In embodiments of the present method, the torches contact the coal, andare operated at a temperature sufficient to induce the spontaneouscombustion of the coal, which is about 10,000° F. (about 5,540° C.), andat this temperature we take all elements to their molecular state. Thetemperature in PPC 10 may be sustained by minimal energy input from thecoal.

Optionally, the concentration of oxygen supplied to PPC 10 may be usedto regulate and maintain the ratio of CO to CO+CO₂ in a desirable range,e.g., between about 20% and about 45%, which prevents or minimizes theformation of soot. Also optionally, water 85 may be added to the gasflow to maintain the temperature of the gas discharged from the PPC 10within a desired temperature range, e.g., from about 2,000° F. (about1,100° C.) to about 2,400° F. (about 1,300° C.), or higher, up to thepractical limit of the highest temperature that the downstream equipmentcan withstand.

During combustion of the coal in the PPC 10, about ninety percent (90%)of the ash components of the coal are melted down into a glassy slag 88by the torches, and the remainder becomes inorganic particulatesentrained in the gas stream. The ash combustion product may not beelectrically conducting until it is melted. To effect the requiredmelting, a dual-mode plasma torch may be operated initially innon-transferred-arc mode until the work piece is molten and conducting,and then switched to non-transferred mode. The plasma gas may beintroduced tangentially so as to produce swirl, thereby stabilizing theflow.

In certain embodiments, the PPC 10 is configured to produce mixing ofthe coal feed 75, treatment gas 80 and water 85 to facilitate completecombustion. The slag resulting from combustion of the ash is melted andcollects at the bottom of the PPC 10, which acts as a crucible. Incertain embodiments, the crucible is rotated as, in, or by a centrifuge.The rotation serves to distribute heat from the torch over the moltenslag and to hold, by centrifugal force, the molten slag away from theaxis of rotation. Rotation of the crucible allows the slag to be removedfrom the bottom of the crucible by slowing its rotation. When sufficientslag has accumulated in the processing chamber it is removed, cooled andallowed to solidify in a shape convenient for disposal or use asbuilding material. Any heavy metals present in the slag are locked inthe leach-resistant glassy slag. An air lock may be used to remove theslag mold and the slag therein.

During the combustion of coal in PPC 10, certain chemicals andcontaminants may be present or formed. If desired or necessary, the PPC10 may be maintained at a negative pressure of, for example, about 25 to50 mbar, to prevent release of contaminants from the PPC. Accordingly,the hot gas stream may comprise, for example, gases such as carbonmonoxide (CO), carbon dioxide (CO₂), hydrogen (H₂), and combinations ofthe foregoing; as well as toxic and/or environmentally hazardouscompounds such as nitrogen oxides (“NO_(x)”), sulfur oxides (“SO_(x)”),dioxin, polychlorinated dibenzodioxins (“dioxins”), dioxin-likecompounds (“DLCs”), polychlorinated dibenzofurans (“furans”),polychlorinated biphenyls (“PCBs”), volatile organic compounds (“VOCs”)acids, (e.g., hydrochloric acid (HCl), nitric acid (HNO₃), sulfuric acid(H₂SO₄), and the like), and combinations of the foregoing. The majorityof these chemicals and contaminants that are formed during combustionare destroyed after formation during the typically 2 second residencetime in the primarily processing chamber 10.

After combustion of the coal in PPC 10, the resulting gas stream O isdischarged into first HRSG 20. No produced gas is vented to theatmosphere from the PPC, but instead all gas is delivered to the HRSG.The HRSGs are capable of receiving the hot gas stream from the PPCswithout suffering appreciable degradation. That is, the HRSGs arecapable of withstanding the temperature, pressure, corrosive chemicals,and the like, to which they may be subjected when contacting the hotgas. To assist in accommodating the elevated temperatures, it may bebeneficial to line portions of the HRSG with ceramic. One exemplary HRSGis a heat-recovery boiler manufactured by NEM (Leiden, the Netherlands).The first HRSG 20 includes an inlet 22 for receiving thecontaminant-containing gas stream O (hereinafter “gas stream O”)discharged from the PPC 10 at a first temperature T₁, and an outlet 24for discharging gas stream O into the SPC 30 at a temperature T₂ that islower than T₁. In the first HRSG 20, heat is extracted from gas stream Ousing a heat exchanger for later use in electricity production,discussed in greater detail below. The amount of heat available forexchange in the first HRSG can vary depending upon various factorsincluding, but not limited to, the configuration of the system, the sizeof the PPC 10, the rate of coal input, and the processing conditions inPPC 10.

The SPC 30, like the PPC 10, is capable of withstanding the processingconditions (i.e., temperature, pressure, corrosion, and the like) towhich it is subjected, and further is adapted to remove any contaminantsremaining after combustion of the coal in the PPC 10. One example ofsuch a system for treating the gas stream P is the PACT system asdiscussed above.

SPC 30 is operated in the same manner as PPC 10. The treatment gas 90and optionally water 95 are simultaneously supplied to SPC 30 at apredetermined flow rate and concentration, while the gas stream P flowsinto the chamber inlet 32 from the outlet 24 of the first HRSG 20, andthe torches heat the gas. An SPC residence time of two seconds isestimated to suffice for the completion of combustion. The addition ofwater in the SPC 30 to the gas stream can be used to maintain and/orcontrol the temperature of the gas in the SPC 30. In some embodiments,it may be desirable to maintain a temperature of about 2,400° F. toabout 2,900° F. (about 1,300° C. to about 1,600° C.).

In SPC 30, treatment gas 90 can react with certain contaminants in thewaste stream to produce a treated gas stream Q from which dioxins,furans, the majority of NO_(R), and the majority of particulate matter(e.g., ash) suspended in the gas stream P have been removed, as well asnon-toxic reaction products and/or by-products. See Examples 1-5, below.For example, during treatment in SPC 30, any remaining carbon monoxideand hydrogen in the gas stream P are converted to carbon dioxide andwater vapor. Compared the chemical compositions of gas streams P and Qin Tables 3-5, 7 and 8, below. Such a conversion is accompanied by therelease of the remaining chemical energy stored in the gas, and may beassisted by the addition of oxygen to the gas. The auto-ignitiontemperature for CO is about 1,100° F. (about 593° C.). Therefore, it maybe desirable to use a spark or flame in the SPC 30 to initiatecombustion. A non-transferred plasma torch may be used for this purpose.

After treatment in SPC 30, treated gas Q, at temperature T₃, isdischarged into the inlet 42 of the second HRSG 40. Second HRSG 40 isfluidly connected to the outlet 34 of SPC 30, and is adapted to receivetreated gas stream Q and to discharge the treated gas stream R, at afourth temperature T₄, lower than T₃, into the inlet 52 of quenchchamber 50. Similar to PPC 10, and depending upon various factorsincluding, but not limited to, the configuration of the system, the sizeof the PACT system, the rate of coal input, and the processingconditions in SPC 30, the amount of heat available for exchange in thesecond HRSG may vary.

Optionally, one or more additional HRSGs (not illustrated) may be usedsequentially with the HRSGs 20 and 40 to capture any residual waste heatfrom the gas stream R. Optionally, the system may comprise one or moreadditional HRSGs (not illustrated) used sequentially with the primaryHRSG 20, all of which perform the same function, which is the transferof heat from the gas stream to the water circulation in the HRSG. Inembodiments employing multiple HRSGs, heat may be extracted at differentpoints along the gas stream. For example, the system comprises two HRSGs20 and 40; the first HRSG 20 extracts heat from the gas stream O as itis discharged from the PPC 10. At this point O, the gas stream containssome corrosive and toxic contaminants; see Examples 1-5, below. Thesecond HRSG 40 extracts heat from the gas stream Q as it is dischargedfrom the SPC 30.

The HRSGs employed in a multiple-HRSG embodiment may differ from oneanother. For example, HRSGs 20 and 40 may differ significantly in thedensity of corrosive and toxic components to which they are subjected,and the HRSGs may have different construction to withstand suchdifferences. When the operating temperature of the processing chamberexceeds the maximum temperature the HRSG can accommodate, FIG. 3illustrates an embodiment in which an additional heat sink, such as anabsorption boiler 15, may be introduced to extract heat from the gasstream between the primarily processing chamber 10 and the HRSG 20. Thegas stream resulting from any additional HRSGs is discharged into eitherthe SPC 30 or the quench chamber 50, if needed, depending upon theirposition. Additional processing chambers and additional heat exchangersmay be added either serially or in parallel.

As shown in FIGS. 2-4, in certain embodiments, the system and methodfurther comprise components for decontaminating the product gas and forgenerating electric power. Power generating section B comprises a steamturbine 100 operatively connected to a generator 110 for generatingelectricity. First and second HRSGs 20, 40 are fluidly connected topower generating section B via the steam turbine 100, separately fromthe fluid connection to the coal treatment system A. The first andsecond HRSGs transfer heat from the gas streams O and Q of section A tothe water supplies 27, and 47 of section B, producing steam for steamsources 29, 49 that are fluidly connected to the steam generator 100.Suitable equipment and systems for implementing the disclosed methodsare available from several manufacturers.

In the quench chamber 50, if needed, the temperature of the treated gasstream R is further reduced to a temperature sufficiently low to preventthe re-formation of contaminants, and to a suitable range to preventdamage to the wet scrubber 60 and/or baghouse 70. In the quench chamber50, water spray is added to the gas stream to rapidly bring thetemperature down to roughly 280° F., or just above the saturationtemperature. FIG. 9 and Example 5 illustrate an embodiment without aquench chamber.

After reduction of the temperature to a suitable range, treated gas S isdischarged from quench chamber 50, into the inlet 62 of wet scrubber 60.In wet scrubber 60, trace VOCs, SO_(x) and remaining particulate matterare removed from treated gas S.

After treatment in wet scrubber 60, the treated gas U is discharged intobaghouse 70, in which the sulfur from the SO_(x) is collected.Thereafter, a “clean” gas stream T comprising cooled down H₂O and CO₂ isdischarged from the baghouse 70. The water can then be separated fromthe CO₂ stream, and the remaining CO₂ can then be captured and isolatedfor EPA approved sequestration or other approved carbon capture andsequestration (CCS) techniques by CO₂ removal system 120.

In an alternative embodiment, illustrated in FIG. 4, treated gas Sdischarged from the quench chamber is directed first to the baghouse 70and thereafter to the wet scrubber 60.

FIG. 2B illustrates an embodiment in which both water and CO₂ can bereturned via separate pathways to the primary processing chamber 10. Inthis embodiment, the temperature of the wet scrubber 60 is maintainedsufficiently low that the water vapor in gas stream U condenses intoliquid. Programmable two-way distribution valve 67 may redirect theliquid water to either the primary processing chamber 10 or its watersources 85, or to a waste water treatment and/or discharge facility 68.The water redirected to the primary processing chamber can be used tosupplement the water 85 added to the gas flow in the chamber, therebyreducing the amount of externally supplied water needed to cool gas flowO leaving the primary chamber. As the returned water has been distilledthrough condensation by the wet scrubber, it contains fewer potentiallycorrosive impurities than from source 85. This has the potential benefitof reducing chemical wear on the upstream components of the steamgenerating system.

FIG. 2C illustrates yet another embodiment, in which water from gas flowO, exiting the primary processing chamber, may condense into a liquid inHRSG 20. This condensation step may result from sufficient heat transferfrom O to the water at inlet 26 of the heat exchanger to cool theeffluent gas from the primary chamber to the condensation point. In thisembodiment, two-way valve 67 may be associated with the water flow fromHRSG 20. Similar to the steps illustrated in FIG. 2B, the liquid watermay then be returned to the primary processing chamber or its watersupply, or to a separate waste water holding section 68. It isunderstood that a similar condensation step may occur in HRSG 40, andthe liquid water returned to the processing chamber 10 or to a wastewater holding section 68 by means of the controllable two-way valve 67.

Illustrated in both FIG. 2B and FIG. 2C is programmable two-waydistribution valve 77 that may selectively direct CO₂ to the baghouse 70for subsequent CO₂ removal at 120, or to the processing chambers, suchas the primary processing chamber 10. The CO₂ returned to the primaryprocessing chamber may improve the efficiency of the combustion process,both by increasing the pressure of the chamber and by decreasing theCO/(CO+CO₂) ratio, thereby reducing soot formation.

FIGS. 2B and 2C further illustrate that both two-way valves 67 and 77are under process control by an automated control system (not shown)through control mechanisms 69 and 79, respectively. In its most basicdesign, such an automatic control system comprises (a) one or a seriesof monitors that measure process parameters including but not limited totemperature, pressure, and input and output material composition, eachof the monitors supply data related to its measured parameter, (b) aprocessor that receives the data from the monitors, and compares thedata values from the parameter monitors to some series of optimalvalues, (c) a tangible memory containing computer-readable instructionsfor the processor to follow, and (d) an actuation mechanism to controlsystem components that may alter the measured process parameters. Forexample, the processor may receive pressure data from a primary chambermonitor and, in response to receiving data indicating that the pressurein the chamber is below a threshold value, the processor may issue acommand to the appropriate valve actuator to cause the valve to directwater and/or carbon dioxide to that chamber.

Temperature and pressure monitors may be located in the primary andsecondary processing chambers. The volume of the water added fromsources 85 and 86 to the primary and secondary processing chambers,respectively, may also be monitored. The composition of the gassesflowing from the various system components—including the effluent O fromthe primary chamber, Q from the secondary processing chamber, S from thequench chamber, U from the wet scrubber and T from the baghouse—may alsobe monitored. Such monitoring may be useful to regulate the amount oftreatment gas 80 or 90 introduced into the primary and secondarychambers, respectively. In addition, the pressure generated by thecombustion processes in both processing chambers 10 and 30 may bemonitored. The reaction mixture composition and pressure in the twoprocessing chambers can provide values to the control system processorto regulate the amount of CO₂ returned to the primary chamber viacontrol mechanism 79 operatively controlled by an actuation mechanism ofthe control system. The amount of returned CO₂ may be used to optimizethe combustion pressure or the CO/(CO+CO₂) ratio. In addition, thetemperatures monitored in the processing chambers can be used toregulate the amount of water injected into them from either the watersources 85 or 86, or from the water returned via two-way valve 67 viacontrol mechanism 69 which is also operatively controlled by anactuation mechanism of the control system.

As noted above, the primary and secondary HRSGs are fluidly connected toa steam turbine 100. The heat extracted from the gas streams O, Q ineach of the primary, secondary and any additional HRSGs, is combined andused to generate steam to drive the steam turbine 100. Aftercondensation of the steam in the turbine 100, water is recycled back toeach of the HRSGs to absorb the heat from the gas streams O, Q. Incertain embodiments, steam 29, 49 produced by HRSG 20 and HRSG 40 drivesa steam turbine 100 that drives a generator of electrical power 110 togenerate electricity in a manner well known in the art.

The system may comprise a variety of equipment configurations, as shownin FIGS. 2-9, to accommodate different space and/or processingrequirements. In addition, as shown in FIG. 4 or FIG. 9 compared to FIG.2, the relative positions of the quench, wet scrubber and baghouse maybe changed, as needed or desired.

FIGS. 5-9 show Sankey Diagrams of the system illustrated in FIG. 4,based on varying equipment and process conditions. As noted above, thepresent method comprises two fluid flows, a first flow carrying theproducts of combustion occurring in the PPC and SPC, and the second flowof the circulation of water cyclically through a HRSG and steam turbine.Examples 1-5 are discussed below. Illustrative calculations were madeusing a proprietary energy balance spreadsheet (Retech Systems LLC,Ukiah, Calif.) that calculates the energy available during thecombustion process for given input materials and an oxidant, such asair, oxygen or mixtures thereof. A balanced system must have the inputand output mass and the input and output energy equal.

The input coal composition used in these Examples is that of the coalfrom the Union Pacific Corporation's Dugout Canyon Mine, Price, Utah.The analysis is provided in Table 1, below, and is indicated by M inFIGS. 1-9.

TABLE 1 Chemical Composition of Input Coal (M) Dugout Canyon Mine, PriceUtah (http://www.uprr.com/customers/energy/coal/utah/soldier.shtml)Total % Ash % lbs/hr kg/hr Carbon 72.20 30083 13646 Hydrogen 5.00 2083945 Oxygen 10.30 4292 1947 Nitrogen 1.40 583 465 Sulfur 0.48 200 91 ASH:10.62 Silica 6.55 61.7 2730 1238 Alumina 1.75 16.5 730 331 Titania 0.060.6 27 12 Ferric oxide 0.32 3.0 133 60 Lime 0.82 7.7 341 155 Magnesia0.18 1.7 75 34 Potassium oxide 0.10 0.9 40 18 Sodium oxide 0.08 0.8 3516 Sulfur trioxide 0.53 5.0 221 100 Phosphorus pentoxide 0.07 0.7 31 14Undetermined 0.15 1.4 62 28 TOTAL 100.00 41,667 18,900

The analysis provided in Table 1 does not indicate the presence ofmercury. However, according to the US Energy InformationAdministration's website, www.eia.doe.gov/oiaf/analysispaper/stb/,mercury levels in coal can vary by region, from 2.04 up to 63.90lbs/trillion Btu. At 12,000 Btu per pound, this equates to 24.5 to 766lbs of mercury per billion pounds of coal. For the purposes of thisstudy, the high end of the range has been assumed. It has further beenassumed that all of this mercury will turn to vapor and travel with thegas through the system and be condensed in two places in the offgassystem: the quench chamber 50, and the wet scrubber 60. The liquidmercury can then be captured and removed by tapping the bottom of thesetwo vessels. Ninety percent is assumed to be captured in the quenchchamber 50 and the remaining 10% in the scrubber 60. Any mercuryremaining in the offgas will thus be below regulatory requirements.

Example 1 Baseline Case: Outlet Temperatures of PPC (T₁) and SPC (T₃)Both=2400° F. (1316° C.)

The outlet temperatures of PPC 10 (T₁) and SPC 20 (T₂) are controlled byadding water from water sources 85, 86 to the respective processingchambers. The mass flow rates in kilograms per hour (kg/h) of all inputsand outputs are shown in Table 2 for the slag chemical composition N,and Table 3, for the chemical composition of the gas flow at points O,P, Q, R, S, T, and U indicated in the schematic diagram of FIG. 5.

In this Example, the coal feed 75 is taken as 18,900 kg/h of coal havingthe composition M given in Table 1, above. The treatment gas 80 input tothe primary processing chamber 10 is 28,900 kg/h O₂, and the water 85input to the primary processing chamber 10 is 41,800 kg/h H₂O.

Given these inputs for a primary processing chamber 10 of volume 5,000ft³ (141,584 l) and a secondary processing chamber 30 of volume 10,100ft³ (286,000 l), the slag 88 has the composition N, summarized in Table2, below.

TABLE 2 Slag Chemical Composition (N), kg/h Silica 1,110 Magnesia 30.7Lime 139 Iron Oxide 54.2 Alumina 298 Other 170

The treatment gas input 90 to the secondary processing chamber 30 is21,334 kg/h O₂, and the water input 86 to the secondary processingchamber 30 is 820 kg/h H₂O. The water input 87 to the quench chamber 50is 21,467 kg/h H₂O. The quench chamber 50 inlet temperature, T₅, is 658°F. (328° C.), and the quench chamber 50 outlet temperature, T₆, is 260°F. (127° C.). The mercury recovery at the quench chamber 50 is 1.31×10⁻²kg/h, and 1.45×10⁻² kg/h at the wet scrubber 60.

The calculated analysis of the chemical composition of the gas flow ispresented in Table 3, below, for the following points of the process:

-   -   primary processing chamber 10 outlet gas, O;    -   first HRSG 20 outlet gas, P;    -   secondary processing chamber 30 outlet gas, Q;    -   second HRSG 40 outlet gas, R;    -   quench chamber 50 outlet gas, S;    -   wet scrubber 60 outlet gas, U;    -   baghouse 70 outlet gas, T.

TABLE 3 Gas Chemical Composition, kg/h O P Q R S T U CO₂ 3.22 × 10⁴ 4.90× 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ CO 1.13 ×10⁴ 6.00 × 10²  0 0 0 0 0 O₂ 0 0 8.24 × 10³ 8.20 × 10³ 8.20 × 10³ 8.20 ×10³ 8.20 × 10³ N₂ 1.24 × 10³ 1.24 × 10³ 1.24 × 10³ 1.24 × 10³ 1.24 × 10³1.24 × 10³ 1.24 × 10³ H₂O 4.20 × 10⁴ 3.51 × 10⁴ 5.03 × 10⁴ 5.03 × 10⁴7.18 × 10⁴ 7.18 × 10⁴ 1.67 × 10³ SOx 1.79 × 10² 1.81 × 10² 1.82 × 10²2.26 × 10² 2.27 × 10² 2.27 × 10² 2.27 × 10¹ H₂ 8.36 × 10² 1.61 × 10³  00 0 0 0 Hg 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻²1.45 × 10⁻² 0 Inorg. Part. 2.01 × 10² 2.01 × 10² 2.01 × 10² 2.01 × 10²2.01 × 10² 2.01 × 10² 1.005 NO_(x) 1.94 × 10⁻³ 0 15.60 1.55 × 10⁻³ 3.00× 10⁻⁵ 3.00 × 10⁻⁵ 3.00 × 10⁻⁵

The basic condition of this Example is that the outlet temperatures ofthe primary processing chamber 10 (T₁) and the secondary processingchamber 30 (T₃) are both equal to 2400° F. (1316° C.). The resultingoutlet temperatures of the first HRSG 20 (T₂) and the second HRSG 40(T₄) are both 658° F. (328° C.).

Example 2 Outlet Temperature of PPC (T1)=2800° F. (1538° C.)

This study assumes that components downstream of the primary processingchamber 10 can tolerate an outlet temperature of the PPC, T₁, of 2800°F. (1538° C.); less water is thus required to control the temperature.This Example also differs from Example 1 in that no water is added inthe SPC 20; the outlet temperature of the SPC, T₃, only reaches 2568° F.(1409° C.). The mass flow rates in kilograms per hour (kg/h) of allinputs and outputs are shown in Table 2, above, for the slag chemicalcomposition N, and Table 4, below, for the chemical composition of thegas flow at points O, P, Q, R, S, T, and U indicated in the schematicdiagram of FIG. 6.

In this Example, the coal feed 75 is taken as 18,900 kg/h of coal havingthe composition M given in Table 1, above. The treatment gas 80 input tothe primary processing chamber 10 is 28,900 kg/h O₂, and the water 85input to the primary processing chamber 10 is reduced to 34,800 kg/hH₂O. The primary processing chamber 10 has a volume 5,000 ft³ (141,584l) and the secondary processing chamber 30 has a volume 10,100 ft³(286,000 l). The slag 88 has the composition N, summarized in Table 2,above.

The treatment gas input 90 to the secondary processing chamber 30 is20,800 kg/h O₂, and the water input 86 to the secondary processingchamber 30 is 0 kg/h H₂O. The water input 87 to the quench chamber 50 is19,500 kg/h H₂O. The quench chamber 50 inlet temperature, T₅, is 658° F.(328° C.), and the quench chamber 50 outlet temperature, T₆, is 260° F.(127° C.). The mercury recovery at the quench chamber 50 is 1.31×10⁻²kg/h, and 1.45×10⁻² kg/h at the wet scrubber 60.

The calculated analysis of the chemical composition of the gas flow ispresented in Table 4, below, for the points of the process O, P, Q, R,S, U, and T, as in Example 1.

TABLE 4 Gas Chemical Composition, kg/h O P Q R S T U CO₂ 2.95 × 10⁴ 4.90× 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ CO 1.30 ×10⁴ 7.19 × 10²  0 0 0 0 0 O₂ 0 0 7.68 × 10³ 7.64 × 10³ 7.64 × 10³ 7.64 ×10³ 7.64 × 10³ N₂ 1.24 × 10³ 1.24 × 10³ 1.24 × 10³ 1.28 × 10³ 1.28 × 10³1.28 × 10³ 1.28 × 10³ H₂O 3.70 × 10⁴ 2.91 × 10⁴ 5.03 × 10⁴ 4.33 × 10⁴6.29 × 10⁴ 6.29 × 10⁴ 1.67 × 10³ SO_(x) 1.79 × 10² 1.81 × 10² 1.82 × 10²2.26 × 10² 2.27 × 10² 2.27 × 10² 2.27 × 10¹ H₂ 7.10 × 10² 1.60 × 10³  00 0 0 0 Hg 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻³1.45 × 10⁻³ 0 Inorg. Part. 2.01 × 10² 2.01 × 10² 2.01 × 10² 2.01 × 10²2.01 × 10² 2.01 × 10² 1.005 NO_(x)  4.6 × 10⁻² 0 22.4 1.53 × 10⁻³ 3.00 ×10⁻⁵ 3.00 × 10⁻⁵ 3.00 × 10⁻⁵

The basic condition of this Example is that the outlet temperatures ofthe primary processing chamber 10 (T₁) 2800° F. (1538° C.). Theresulting outlet temperatures of the first HRSG 20 (T₂) and the secondHRSG 40 (T₄) are both 658° F. (328° C.).

Example 3 Rapid Quench

This study examines the expected performance if a rapid quench of thegases is required to prevent the formation of dioxins or furans, a stepthat would be likely to be required if chlorine is present in the coalfeed. The mass flow rates in kilograms per hour (kg/h) of all inputs andoutputs are shown in Table 2, above, for the slag chemical compositionN, and Table 5, below, for the chemical composition of the gas flow atpoints O, P, Q, R, S, T, and U indicated in the schematic diagram ofFIG. 7.

In this Example, the coal feed 75 is taken as 18,900 kg/h of coal havingthe composition M given in Table 1, above. The treatment gas 80 input tothe primary processing chamber 10 is 28,900 kg/h O₂, and the water 85input to the primary processing chamber 10 is 41,800 kg/h H₂O. Theprimary processing chamber 10 has a volume 5,000 ft³ (141,584 l) and thesecondary processing chamber 30 has a volume 10,100 ft³ (286,000 l). Theslag 88 has the composition N, summarized in Table 2, above.

The treatment gas input 90 to the secondary processing chamber 30 is20,800 kg/h O₂, and the water input 86 to the secondary processingchamber 30 is 0 kg/h H₂O. The water input 87 to the quench chamber 50 is19,500 kg/h H₂O. The quench chamber 50 inlet temperature, T₅, is 658° F.(328° C.), and the quench chamber 50 outlet temperature, T₆, is 260° F.(127° C.). The mercury recovery at the quench tower 50 is 1.31×10⁻²kg/h, and 1.45×10⁻² kg/h at the wet scrubber 60.

The calculated analysis of the chemical composition of the gas flow ispresented in Table 5, below, for the points of the process O, P, Q, R,S, U, and T, as in Example 1.

TABLE 5 Gas Chemical Composition, kg/h O P Q R S T U CO₂ 2.95 × 10⁴ 4.90× 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 104 5.00 × 10⁴ 5.00 × 10⁴ CO 1.30 ×10⁴ 7.19 × 10²  0 0 0 0 0 O₂ 0 0 7.68 × 10³ 7.64 × 10³ 7.64 × 103 7.64 ×10³ 7.64 × 10³ N₂ 1.24 × 10³ 1.24 × 10³ 1.24 × 10³ 1.28 × 10³ 1.28 × 1031.28 × 10³ 1.28 × 10³ H₂O 3.70 × 10⁴ 2.91 × 10⁴ 5.03 × 10⁴ 4.33 × 10⁴6.29 × 104 6.29 × 10⁴ 1.67 × 10³ SO_(x) 1.79 × 10² 1.81 × 10² 1.82 × 10²2.26 × 10² 2.27 × 102 2.27 × 10² 2.27 × 10¹ H₂ 7.10 × 10² 1.60 × 10³  00 0 0 0 Hg 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10−31.45 × 10⁻³ 0 Inorg. Part. 2.01 × 10² 2.01 × 10² 2.01 × 10² 2.01 × 10²2.01 × 102 2.01 × 10² 1.005 NO_(X)  4.6 × 10⁻² 0 22.4 1.53 × 10⁻³ 3.00 ×10−5 3.00 × 10⁻⁵ 3.00 × 10⁻⁵

The basic condition of this Example is that the outlet temperatures ofthe primary processing chamber 10 (T₁) 2800° F. (1538° C.). Theresulting outlet temperatures of the first HRSG 20 (T₂) and the secondHRSG 40 (T₄) are both 658° F. (328° C.).

Example 4 Smaller (PACT-8) Size System

This study examines the expected performance a smaller size system,roughly the size of the PACT-8 (Retech Systems LLC, Ukiah, Calif.), thatcan accommodate a coal feed of about 1,000 kg/hr. The mass flow rates inkilograms per hour (kg/h) of all inputs and outputs are shown in Table6, below, for the slag chemical composition N, and Table 7, below, forthe chemical composition of the gas flow at points O, P, Q, R, S, T, andU indicated in the schematic diagram of FIG. 8.

In this Example, the coal feed 75 is taken as 1,000 kg/h of coal havingthe composition M given in Table 1, above. The treatment gas input 80 tothe primary processing chamber 10 is 1,470 kg/h O₂, and the water 85input to the primary processing chamber 10 is 1,900 kg/h H₂O. Theprimary processing chamber 10 has a volume 265 ft³ (7503 l) and thesecondary processing chamber 30 has a volume 500 ft³ (14158 l). The slag88 has the composition N, summarized in Table 6.

TABLE 6 Slag Chemical Composition (N), kg/h Silica 59 Magnesia 1.63 Lime7.36 Iron Oxide 2.87 Alumina 15.8 Other 8.98

The treatment gas input 90 to the secondary processing chamber 30 is1,170 kg/h O₂, and the water input 86 to the secondary processingchamber 30 is 0 kg/h H₂O. The water input 87 to the quench chamber 50 is1,108 kg/h H₂O. The quench chamber 50 inlet temperature, T₅, is 658° F.(328° C.), and the quench chamber 50 outlet temperature, T₆, is 260° F.(127° C.). The mercury recovery at the quench chamber 50 is 6.9×10⁻³kg/h, and 7.7×10⁻⁴ kg/h at the wet scrubber 60.

The calculated analysis of the chemical composition of the gas flow ispresented in Table 7, below, for the points of the process O, P, Q, R,S, U, and T, as in Example 1.

TABLE 7 Gas Chemical Composition, kg/h O P Q R S T U CO₂ 1.66 × 10³ 2.59× 10³ 2.64 × 10³ 2.54 × 10³ 2.54 × 10³ 2.54 × 10³ 2.54 × 10³ CO 6.25 ×10² 3.66 × 10¹ 0 0 0 0 0 O₂ 0 0 4.74 × 10² 4.73 × 10² 4.73 × 10² 3.46 ×10³ 3.46 × 10³ N₂ 7.97 × 10² 7.97 × 10² 7.97 × 10² 7.97 × 10² 7.97 × 10²7.97 × 10² 7.97 × 10² H₂O 1.98 × 10³  1.6 × 10³ 2.35 × 10³ 2.36 × 10³3.46 × 10³ 3.46 × 10³ 3.46 × 10³ SO_(x) 9.49 × 10° 9.59 × 10° 9.62 × 10° 1.2 × 10°  1.2 × 10°  1.2 × 10°  1.2 × 10° H₂ 4.22 × 10¹  8.4 × 10² 0 00 0 0 Hg 7.67 × 10⁻³ 7.67 × 10⁻³ 7.67 × 10⁻³ 7.67 × 10⁻³  7.7 × 10⁻⁴ 7.7 × 10⁻⁴  7.7 × 10⁻⁴ Inorg. Part. 1.06 × 10¹ 1.06 × 10¹ 1.06 × 10¹1.06 × 10¹ 1.06 × 10¹ 1.06 × 10¹ 1.06 × 10¹ NO_(x)   3 × 10⁻⁴ 0 1.03 ×10°   3 × 10⁻⁴   3 × 10⁻⁴   3 × 10⁻⁴   3 × 10⁻⁴

The smaller sizes of the PPC 10 and the SPC 30 in this Example wereassociated with lower values of T₁, 2400° F. (1316° C.), and T₃, 2012°F. (1100° C.). The resulting outlet temperatures of the first HRSG 20(T₂) and the second HRSG 40 (T₄) are both 658° F. (328° C.).

Example 5 Outlet Temperature of HRSG1 (T2)=HRSG2 (T4)=260° F. (127° C.)

This study assumes that outlet temperatures from both HRSGs are 260° F.(127° C.). T₃, only reaches 2568° F. (1409° C.). The mass flow rates inkilograms per hour (kg/h) of all inputs and outputs are shown in Table2, above, for the slag chemical composition N, and Table 4, below, forthe chemical composition of the gas flow at points O, P, Q, R, S, T, andU indicated in the schematic diagram of FIG. 9.

As in Example 1, the coal feed 75 is taken as 18,900 kg/h of coal havingthe composition M given in Table 1, above. The treatment gas input 80 tothe primary processing chamber 10 is 28,900 kg/h O₂, but the water 85input to the primary processing chamber 10 is reduced to 41,000 kg/hH₂O. The primary processing chamber 10 has a volume 5,000 ft³ (141,584l) and the secondary processing chamber 30 has a volume 10,100 ft³(260,500 l). The slag 88 has the composition N, summarized in Table 2,above.

The treatment gas input 90 to the secondary processing chamber 30 is21,300 kg/h O₂, and the water input 86 to the secondary processingchamber 30 is 0 kg/h H₂O. The quench chamber 50 is eliminated. Mercuryrecovery at the second HRSG is 1.31×10⁻² kg/h, and 1.45×10⁻² kg/h at thewet scrubber 60.

The calculated analysis of the chemical composition of the gas flow ispresented in Table 8, below, for the points of the process O, P, Q, R,U, and T, as in Example 1.

TABLE 8 Gas Chemical Composition, kg/h O P Q R T U CO₂ 3.22 × 10⁴ 4.90 ×10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ 5.00 × 10⁴ CO 1.13 × 10⁴   6 × 10²0 0 0 0 O₂ 0 0 8.17 × 10³ 8.13 × 10³ 8.13 × 10³ 8.13 × 10³ N₂ 1.24 × 10³1.24 × 10³ 1.23 × 10³ 1.24 × 10³ 1.24 × 10³ 1.24 × 10³ H₂O 4.20 × 10⁴3.48 × 10⁴ 4.95 × 10⁴ 4.95 × 10⁴ 4.95 × 10⁴ 1.67 × 10³ SO_(x) 1.79 × 10²1.81 × 10² 1.82 × 10² 2.27 × 10² 2.27 × 10² 2.27 × 10¹ H₂ 8.36 × 10²1.65 × 10³ 0 0 0 0 Hg 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻² 1.45 × 10⁻²1.45 × 10⁻³ 0 Inorg. Part. 2.01 × 10² 2.01 × 10² 2.01 × 10² 2.01 × 10²2.01 × 10° 1.005 NO_(x) 1.94 × 10⁻³ 0 9.06   4 × 10⁻⁵   4 × 10⁻⁵   4 ×10⁻⁵

Baseline energy-balance calculations indicate that desirabletemperatures for the gas entering the HRSGs may range from about 2,000°F. to about 2900° F. (about 1,100° C. to about 1,600° C.), and thatdesirable temperatures for the gas exiting the HRSGs may range fromabout 258° F. to about 1500° F. (about 120° C. to about 860° C.).

In an alternative embodiment, the gas output from the PPC 10 may bedischarged directly into a turbine that is adapted to receive gases atthe temperatures resulting after oxidation, e.g., about 10,000° F.(about 5,540° C.), without decreasing the temperature of the gas to atemperature that the HRSGs can accommodate.

Example 6 Treatment of Thermal Waste Gas

The present disclosure is directed to a method and system for generatingenergy from a gaseous waste stream, such as gaseous waste streamsresulting from certain industrial processes including, but not limitedto, power plants, industrial manufacturers, industrial facilities, wasteto power plants, generators, steel mills, incinerators, factories,landfills, methane conversion plants, landfill flares, smokestacks,medical waste facilities, and the like. Such gaseous waste streams maycomprise, for example, gases such as carbon monoxide (CO), carbondioxide (CO₂), hydrogen (H₂), and combinations of the foregoing; andadditionally toxic and/or environmentally hazardous compounds such asnitrogen oxides (“NO_(x)”), sulfur oxides (“SO_(x)”), dioxin,polychlorinated dibenzodioxins (“dioxins”), dioxin-like compounds(“DLCs”), polychlorinated dibenzofurans (“furans”), polychlorinatedbiphenyls (“PCBs”), acids (e.g., hydrochloric (HCl), nitric (HNO₃),sulfuric (H₂SO₄), and the like), and combinations of the foregoing.

FIG. 10 is a flow-chart illustrating one exemplary system and methodaccording to the present disclosure, which comprises a gaseous treatmentsection A operatively connected to a power generating section B. Asshown, gaseous treatment section A comprises a first heat recovery steamgenerator 20 (“first HRSG”), a primary processing chamber 10, a secondHRSG 40, a quench chamber 50, a wet scrubber 60, and a baghouse 70, allfluidly connected. A source of a treatment gas 80, such as O₂, isfluidly connected to the primary processing chamber 10. Suitableequipment and systems for implementing the disclosed methods areavailable from several manufacturers.

Power generating section B comprises a steam turbine 100 operativelyconnected to an electric generator 110, for generating electricity.First and second HRSGs 20, 40 are fluidly connected to power generatingsection B via the steam turbine 100, separately from the fluidconnection to the coal treatment system.

In the present method, a contaminant-containing gas stream O, from acontaminant-containing gas source 130, is continuously introduced intothe first HRSG 20. The first HRSG 20 comprises an inlet 22 for receivingthe gas stream O at a first temperature T₁, and an outlet 24 fordischarging gas stream P, at a temperature T₂ that is lower than T₁,into the primary processing chamber 10. In the first HRSG 20, heat isextracted from gas stream O for later use in energy production, whichwill be discussed in greater detail below.

Optionally, one or more additional HRSGs (not illustrated) may be usedsequentially with the primary HRSG 20 to utilize any residual waste heatfrom the primary HRSG 20, and the gas stream resulting from anyadditional HRSGs is discharged into the primary processing chamber 10.

Primary processing chamber 10 is capable of treating gas stream P suchthat the majority of contaminants and particulates are removedtherefrom. Accordingly, primary processing chamber 10 is capable ofwithstanding the processing conditions (i.e., temperature, pressure,corrosion, and the like), under which such treatment takes place. Incertain embodiments, the PPC 10 is configured to produce mixing of thecoal feed 75, treatment gas 80 and water 85 to facilitate completecombustion. One exemplary system is a plasma arc centrifugal treatment(PACT) system available from Retech Systems, LLC, in Ukiah, Calif.)comprising one or more non-transferred arc plasma torches fitted withgas backflow collars. Non-transferred arc plasma torches house bothelectrodes inside the torch, and the plasma extends beyond the end ofthe torch as a result of high gas flow through the torch, even thoughthe electrodes are inside the torch. For ease of discussion, the terms“torch” or “torches” will be used hereinafter to refer tonon-transferred arc plasma torches. FIGS. 11A and 11B are schematicdiagrams of a non-transferred mode plasma arc torch, 300, and atransferred mode plasma arc torch 350.

FIG. 11A and FIG. 11B are schematic diagrams of a non-transferred plasmaarc torch 300 and a transferred plasma arc torch 350. FIG. 10A shows thefront electrode 310, the rear electrode 312, insulator 318, the arc gassupply 320 and the plasma gas 330. FIG. 11B shows the electrode 314, thenozzle 360, insulator 318, the swirl ring 316, the arc gas supply 320and the plasma gas 330 contacting the melt 370, which is maintained atelectrical ground.

According to the present method, the gas stream P is continuouslyintroduced into the primary processing chamber 10, and the treatment gas80 is simultaneously supplied to primary processing chamber 10 at apredetermined flow rate and concentration, while the torches heat boththe gaseous waste stream and the treatment gas contained in the chamber.In primary processing chamber 10, treatment gas 80 can react withcertain contaminants in the waste stream to produce a treated gas streamQ from which dioxins, furans, the majority of NO_(R), and the majorityof particulate matter (e.g., ash) suspended in the gas stream P havebeen removed, and also comprising non-toxic reaction products and/orby-products. For example, during treatment in primary processing chamber10, CO and H₂ are oxidized such that the treated gas stream comprisescarbon dioxide (CO₂) and water (H₂O).

After treatment in primary processing chamber 10, treated gas Q, attemperature T₃ is discharged into second HRSG 40. Second HRSG 40 isfluidly connected to the outlet of primary processing chamber 10, and isadapted to receive treated gas stream Q and to discharge the treated gasstream R at a fourth temperature T₄, lower than T₃, into the quenchchamber 50.

In the quench chamber 50, the temperature of the treated gas stream R isfurther reduced to a temperature sufficiently low to prevent there-formation of contaminants, and to a suitable range to prevent damageto the wet scrubber 60 and/or baghouse 70. After reduction of thetemperature to a suitable range, treated gas S is discharged from quenchchamber 50 into the wet scrubber 60. In wet scrubber 60, VOCs, SO_(R)and remaining particulate matter are removed from treated gas S, and thetreated gas U is discharged into baghouse 70, in which the sulfur fromthe SO_(x) is collected.

Thereafter, a “clean” gas stream T comprising cooled down H₂O and CO₂ isdischarged from the system A. The water can then be separated and theCO₂ stream can then be isolated for EPA approved sequestration or otherapproved carbon capture and sequestration (CCS) techniques for CO₂removal in CO₂ removal system 120.

FIG. 12 is a schematic diagram of certain features of an embodiment of aprimary processing chamber showing a transferred plasma arc torch 350and a centrifuge portion 400. The transferred plasma arc torch 350includes water-cooled electrode 315, nozzle 360, swirling plasma gas334, and plasma arc terminations 336. The slag bath 372 is held awayfrom the slag exit 16 in the centrifuge floor 420 by the rotation of thecentrifuge 400.

FIG. 13 is a diagram of a vertical embodiment showing the primaryprocessing chamber 10 in fluid communication with the first HRSG 20having inlet 22 and outlet 24, the secondary processing unit 30 havinginlet 32 and outlet 34 and the second HRSG 40 having inlet 42 and outlet44. The primary processing chamber 10 has slag outlet 16, gas outlet 18,a transferred plasma arc torch 350 and a centrifuge portion 400. Slagcollection containers 89 can be positioned below the slag outlet 16.

FIGS. 14A, 14B and 14C are schematic diagrams of an embodiment of ahorizontal processing chamber layout for primary and secondaryprocessing chambers and two HRSGs according to the present disclosure.FIG. 14A shows a cross-section view with a modular PACT 500 as a regionof the primary processing chamber 10; the PACT 500 includes a slagoutlet 16, centrifuge portion 400, gas outlet 18, and a transferredplasma arc torch 350. Slag collection containers 89 can be positionedbelow the slag outlet 16. FIG. 14B is a longitudinal section viewshowing the primary processing chamber 10 in fluid communication withthe first HRSG 20 having inlet 22 and outlet 24, the secondaryprocessing unit 30 having inlet 32 and outlet 34 and the second HRSG 40having inlet 42 and outlet 44. FIG. 14C is a schematic diagram of across-section view showing a primary processing chamber 10 in fluidcommunication with a plurality of modular PACTs 500.

While the disclosure has been described with reference several exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromthe essential scope thereof. Therefore, it is intended that thedisclosure not be limited to the particular embodiments disclosed as thebest mode contemplated for carrying out this disclosure, but that thedisclosure will include all embodiments falling within the scope of theappended claims.

Ranges disclosed herein are inclusive and combinable (e.g., ranges of“up to about 25 weight percent (wt. %), with about 5 wt. % to about 20wt. % desired, and about 10 wt. % to about 15 wt. % more desired,” areinclusive of the endpoints and all intermediate values of the ranges,e.g., “about 5 wt. % to about 25 wt. %, about 5 wt. % to about 15 wt.%”, etc.). Unless defined otherwise, technical and scientific terms usedherein have the same meaning as is commonly understood by one of skillin the art to which this disclosure belongs.

Throughout the application, it should be noted that the terms “first”and “second,” “primary” and “secondary,” and the like herein, do notdenote any order or importance, but rather are used to distinguish oneelement from another, and the terms “a” and “an” herein do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced items. Similarly, it is noted that the terms “bottom”and “top” are used herein, unless otherwise noted, merely forconvenience of description, and are not limited to any one position orspatial orientation. In addition, the modifier “about” used inconnection with a quantity is inclusive of the stated value and has themeaning dictated by the context (e.g., includes the degree of errorassociated with measurement of the particular quantity).

1. A system for generating steam comprising: a primary processingchamber comprising at least one plasma arc torch that heats at least aportion of the primary processing chamber to a temperature of from about5540° C. to 11,080° C.; a feed source configured to deliver acarbonaceous material feed to the primary processing chamber; a firsttreatment gas source configured to deliver a treatment gas to theprimary processing chamber; a first water source configured to deliverwater to the primary processing chamber; a first heat recovery steamgenerator that is fluidly connected to the primary processing chamberand configured to receive a product gas stream comprising at least watervapor from the primary processing chamber; a scrubber configured toreceive and process the product gas stream; a first programmable valvehaving a first control mechanism configured to selectively direct aportion of the carbon dioxide in the product gas stream back to theprimary processing chamber and a portion of the carbon dioxide to abaghouse; and a second programmable valve having a second controlmechanism configured to selectively direct a portion of the water backto the primary processing chamber and a portion of the water to a waterfacility, wherein the water is condensed from the product gas stream. 2.The system of claim 1 further comprising: a secondary processing chamberconfigured to receive the product gas stream from the first heatrecovery steam generator, the secondary processing chamber comprising atleast one plasma arc torch that heats at least a portion of thesecondary processing chamber to a temperature of from about 5540° C. to11,080° C.; a second treatment gas source configured to deliver atreatment gas to the secondary processing chamber; a second water sourceconfigured to deliver water to the secondary processing chamber; and asecond heat recovery steam generator that is fluidly connected to thesecondary processing chamber and configured to receive a product gasstream from the second processing chamber and deliver the product gasstream to the scrubber.
 3. The system of claim 2 further comprising: asteam turbine configured to receive steam that is generated by the firstheat recovery steam generator and by the second heat recovery steamgenerator.
 4. The system of claim 2 further comprising: an automatedcontrol system, the automated control system comprising: a) a pluralityof monitors each configured to measure a process parameter and providedata thereof; b) a processor in data communication with the plurality ofmonitors; and c) at least two actuation mechanisms in data communicationwith the processor; wherein the first of the at least two actuationmechanisms is in operative communication with the first controlmechanism of the first programmable valve, and the second of the a leasttwo actuation mechanisms is in operative communication the secondcontrol mechanism of the second programmable valve.
 5. The system ofclaim 4: wherein the data provided by each of the plurality of monitorscomprises at least one of temperature, pressure, carbon dioxidecomposition, water volume, and gas flow.
 6. The system of claim 5:wherein at least one of the plurality of monitors provides a firstpressure data associated with the primary processing chamber; at leastone of the plurality of monitors provides a carbon dioxide compositiondata associated with the product gas stream from the primary processingchamber; and wherein the first of the at least two actuation mechanismsis controlled at least in part by the processor based on at least one ofthe carbon dioxide composition data, and the pressure data.
 7. Thesystem of claim 5: wherein at least one of the plurality of monitorsprovides a first water volume data associated with the water deliveredby the first water source; at least one of the plurality of monitorsprovides a second water volume data associated with the water deliveredby the second water source, and at least one of the plurality ofmonitors provides temperature data associated with the primaryprocessing chamber; and wherein the second of the at least two actuationmechanisms is controlled at least in part by the processor based on atleast one of the first water volume data, the second water volume data,and the temperature data.
 8. The system of claim 7: wherein the water iscondensed from the product gas stream in the wet scrubber.
 9. The systemof claim 7: wherein the water is condensed from the product gas streamin either the first heat recovery steam generator or the second heatrecovery steam generator.
 10. A method for generating steam comprising:providing a continuous supply of a carbonaceous material; combusting thecarbonaceous material in a first processing chamber having a firstplasma arc torch in the presence of a first treatment gas and water toprovide a first product gas stream, the first product gas streamcomprising at least water and carbon dioxide; recovering heat from thefirst product gas stream in a first heat recovery steam generator toproduce a first steam output; processing the first product gas stream ina second processing chamber having a second plasma arc torch in thepresence of a second treatment gas and water to provide a second productgas stream comprising at least carbon dioxide and substantially free ofcarbon monoxide and hydrogen; recovering heat from the second productgas stream in a second heat recovery steam generator to produce a secondsteam output; directing at least a portion of the carbon dioxide to thefirst processing chamber; and, directing at least a portion of the waterto the first processing chamber; wherein each of the first plasma torchand the second plasma torch generates heat from 5540 C to 11,080 C;wherein the carbon dioxide is directed to the first processing chambervia a first programmable valve having a first control mechanism; and,wherein the water is directed to the first processing chamber via asecond programmable valve having a second control mechanism.
 11. Themethod of claim 10 further comprising: processing the second streamoutput in a wet scrubber to provide a wet scrubber output.
 12. Themethod of claim 11: wherein the wet scrubber output comprises at leastwater and carbon dioxide.
 13. The method of claim 11 further comprising:providing a plurality of monitors each configured to measure at leastone of a plurality of process parameters and provide data thereof to aprocessor; and controlling the first control mechanism and the secondcontrol mechanism by the processor, based at least in part on the dataprovided by the plurality of monitors.
 14. The method of claim 13:wherein the plurality of process parameters measured by the monitorscomprise at least one of temperature, pressure, carbon dioxidecomposition, water volume, and gas flow.
 15. The method of claim 13:wherein the plurality of monitors measure the process parameters in atleast one of the first processing chamber, the first product gas stream,the first heat recovery steam generator, the first steam output, thesecond processing chamber, the second product gas stream, and the secondstream output.